Controlling alternating-current motors.



Patented Nov. 25, 1902.

C; P. STEINMETZ. I CONTROLLING ALTERNATING' CURRENT MOTURS.

y Appxicasion med June 7, 1899.)

(No Models) isalais.

MTNEEEES.

No. 7|4,4u. Patented Nov. 25, |902.

c. P. sTEmMErz. CUNTROLLING ALTEHNATING CURRENT NITOBS.A

(Application led June 7, 1899.)

(No Model.) 2 Sheets-Sheet 2.

15-5 5 F C j UNITED STATES PATENT OFFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

CONTROLLING ALTERNATlNG-CURRENT MOTORS.

SPECIFICATION forming part of Letters Patent No. 714,411, dated November25, 1902- Applieation led June 7,1899. Serial No. 719,696. (No model.)

To all whom it may concern: a switching mechanism made in accordanceBeit knownthat I, CHARLES P. STEINMETZ, with my invention. Fig. 2 is aview of the a citizen of the United States, residing at same partly insection. Fig. Sis a diagram Schenectady, county of Schenectady, State ofof circuits, while Figs. 4 to 8, inclusive, repre- 55 5 New York, haveinvented certain new and sent changes in circuit connections eectedusefullmprovementsin ControllingAlternatby the switching mechanismillustrated in ing-Current Motors, of which the following is Fig. 3.aspecification. My invention in its details will be more In controllingalternating-current motors clearly apprehended by first describing, 6o1o considerable difficulty is encountered in the briefly, its generalfeatures, and this can best endeavor to extinguish effectually the arcsbe done by referring to Figs. 4E to 8, inclusive, which result fromopening the motor-circuits. which serve to illustrate the same in ageneral Because of the nature of the alternating arc way. the magneticblow-out is not always appli- Fig. 4 indicates connections corresponding65 cable, While the employment of other meansto the off position of theswitch, both primary Such, for example, as breaking the circuit unandsecondary windings A and B, respecder oil or other insulating iiuid-isattended tively, being open-circuited, as indicated. As with manydisadvantages. For these reathe controller-handle is turned the rstconsons I have devised a means for controlling nection made causes alarge resistance R to zo alternating-current motors which does away beinsertedin series with the windings of the with the necessity for anyspecial means for inducing member A, as shown in Fig. 5, whileextinguishing arcs which may be formed. a further movement of thecontroller-handle My invention is more especially valuable causes theresistance to be gradually cut out where such motors for any reason havea until, as shown in Fig. 6, the free ends of the z 5 largemagnetizing-current. primary winding are connected together di- Myinvention in its concrete form, as hererectly, at which time only themagnetizingin illustrated, consists of a switching mechcurrent isflowing through the motor and no anism with suitable electricalconnections for torque is exerted by the secondary member. connecting anon-inductive resistance in cir- After having been withdrawn from thepri- 8o 3o cuit first with one member of an inductionmary member thewhole resistance R is inmotor and then in circuit with the othermemserted in series with the secondary B of the ber, the operation beingsuch that on stopping induction-motor. The motor is thus started themotor the resistance is first withdrawn in the ordinary manner, and asit gathers from the windings of the secondary member speed theresistance is gradually cut out by 35 and then placed in circuit withthe primary a further rotation of the controller-handle member. Withresistance thus placed in ciruntil the normal running condition isreached, cuit with a primary member the magnetizingin which theresistance is entirely cut out, as current is reduced to a value sosmall that shown in Fig. S. The function of the startno difliculty isexperienced from arcing when ing resistance for induction-motors is soWell 9c 4o the circuit is opened. It will thus be seen understood thatno explanation of the same that in accordance with my invention the reisnecessary other than to refer to the mansistance which is ordinarilyused for controlner in which the starting resistance is emling the speedand torque of an inductionployed in this particular instance. motorpossesses in this instance an additional In starting the motor no usefulpurpose is 45 function. served by first inserting the resistance in theThe details of my invention will be better primary member and thencutting the same understood by reference to the following deout. It isonly when the connections thus scription, taken in connection with theacdescribed are performed by the controllerin companying drawings,whileits scope will be the reverse order that the manipulation of roo 5opointed out in the claims appended hereto. the resistance with respectto the primary In the drawings, Figure 1 is a plan view of windingbecomes useful.

When running normally, the connections of the motor are as indicated inFig. S, and the first step in putting the motor out of circuit consistsin inserting resistance in the secondary member, as shown in Fig. 7, andthen breaking the circuit of said member, as in Fig. 6. The sameresistance is then gradually cut into the primary winding, as shown inFig. 5, until the magnetiZing-current of the motor has been reduced to aminimum, when the primary circuit is opened, thus leaving both membersopencircuited,as indicated in Fig. 4C. The arrangement of circuitswhereby these changes are effected is indicated diagrammatically in Fig.3, in which @2 @3 denote the three primary windings of the motor and Z9b2 b3 the secondary windings. One end of each of the primary windings @2@3 is connected, respectively, with one ofthe terminals 1 2 3 of thereversingswitch S, by means of which the primary winding as a whole isconnected to the multiphase supply-mains @'ZJ c. When thereversing-switch is thrown in one direction, the terminals l 2 3 areconnected, respectively, to the mains Z) c and by virtue of thisconnection the motor is given a definite direction of rotation, whilewhen the switch is thrown in the opposite direction the terminal 3 is,as before, connected to the main c, while the connections of theterminals l 2, on the other hand, are reversed, the terminal 2 beingconnected to the main and the terminal l to the main b, thus causing anopposite direction of rotation of the motor. The opposite ends of thecoils @2 @3 are connected, respectively, with three angularly-displacediixed contacts @11, @22, and @33, forming part of' the switchingmechanism.

The secondary windings of the motor are indicated at b b2 b3 and areshown with one end of each winding connected together in any suitablemanner and with the free ends connected to fixed contacts b Z122 Z133,forming part of the switching mechanism and located adjacent to thefixed contacts @11,@22, and @33, to which the free ends of the primarywindings are connected. A non-inductive resistance in three sections RR2 R3 is located adjacent to the fixed contacts before mentioned, andeach section of the resistance is connected at intervals in its lengthto suitable contactblocks or contacts arranged concentrically withrespect to the fixed contacts. One end of each section ot' theresistance is connected to a common point, these connections beingindicated in the drawings at r r2 r3, leaving the opposite ends of theresistances normally disconnected. Suitably -insulated contacts 7c k27c3 of conductive material are located adjacent to the contactsconnected tothe respective sections of resistance and with theirsurfaces flush with the surfaces Lof the resistance-contacts, so as toallow the switch-arms which cooperate therewith to move from onecontacttoanother. Theconnectionsbetween the various contacts thusreferred to are effected by means of two sets of bridging-contacts, thetwo sets being individually movable with respect to each other and eachset formed of three bridging-contacts, each of which operates inconjunction with resistance-contacts and with one of the xed contactsconnected to the motor-windings.

The bridging-contacts Z/ Z2 Z3 operate in conjunction, respectively,with the fixed contacts Zt 762 7c3 and are carried on the ends of threearms fixed with respect to each other and simultaneously rotatable bymeans of the controller-handle. One end of each bridgingcontact makesconnection with one of the fixed contacts Zz 7a2 k3 and slides over thesurface of one of the corresponding fixed contacts Z9 522 Z933, asindicated. In a similar manner the bridging-contacts m', m2, and m3 bearupon one of the contact-blocks Zt 7a2 7c3 and upon one of thecorresponding fixed contacts @11, @22, and @33, connected to thewindings of the other member of the motor. The lastdescribed set ofbridging-contacts, as in the case of the first set, is carried byprojecting arms, also rotated by means of the controllerhandle. Thesetwo sets of arms are interrelated in a manner hereinafter to bedescribed. The connections made by the bridging-contacts which arecarried by these arms will, however, be evident from Fig. 3.

In the position of the parts shown both of the windings of the motor areopen-circuited. When the controller-handle is first turned, the set ofbridging-contacts m m2 m3 is rotated in the direction ofthe hands of awatch and moved oft' of the insulated contacts Zt k2 7c3, upon whichthey rest when the motor is out of circuit, and then onto the set ofcontacts connected with the sections of resistance R R2 R3. Vhen thebridging connections are thus shifted, a section of resistance is placedin circuit with each of the primary windings @2 @3. Thus, for example,the coil would be connected through the fixed contact @l to the free endc2 of the resistance R2 and then through the resistance to the neutralpoint o, to which the corresponding ends of the other sections ofresistances are connected. As the controller-handle is moved forward thebridging-contacts m m2 'm3 are moved along over the fixed contactsconnected to the resistance-sections until finally all the resistance isout out, this condition being reached when the bridging-contacts restupon the contacts directly connected with the connections r' r2 r3. Atthis point the arms carrying these bridging-contacts are uncoupled fromthe controller-handle and the other set of arms, carrying the other setof bridgingcontacts, is caused to engage with the handle. Thebridging-contacts Z Z2 Z3 thus set into motion by the further movementof the controller-handle are each connected to one of the windings19'192 b5 of the secondary member and operate to insert resistance inthe secondary member. Thus, for example, when the bridging-contact Z ismoved forward it IOO IIO

passes off of the insulated contact t and onto the first contact of theresistance R', thus connecting the free end of the Winding b3 of thesecondary member of the motor through the resistance R' to the neutralpoint o. In a similar manner the other coils b b2 of the secondarymember are connected through corresponding resistances R2 and R3 to thesame common or neutral point 0. The connections thus made correspond tothe starting connections, in which the primary is connected directlyacross the mains, while the secondary windings are connected togetherthrough a large non -inductive resistance. After the motor starts thecontroller-handle is moved along still farther, thus cutting out thesections of resistance and so increasing the speed of the motor up tothe point where all the resistance is cut out and the terminals of thewindings of the secondary member are connected directly together throughthe medium of the bridging-contacts and the connecting wires or circuitsr' r2 r3. This corresponds to the running connection of the motor. Indisconnecting the motor from circuit the operations thus described aregone through with in the reverse order. After the resistance has beencut out of the secondary member the same resistance is then graduallycut into circuit in the primary member, and the circuits of the lattermember are then broken, the break taking place as the bridging-contactsm m2 m3 pass olf of the contacts connected with the resistance onto theinsulated contacts 7c' 7a2 7c3, upon which they rest in the olf positionof the controller. By thus utilizing the motor-starting resistance thespark which takes place upon opening-the primary circuit is very greatlyreduced and so much so as to cause but little if any trouble due toarcing. i

The switch mechanism which I employ for the purpose of eecting theabove-described dissimultaneous movement of the two sets ofbridging-contacts is shown in Figs. l and 2. At 4 is shown a shaftsecured to the top 5 of the resistance-box or other support for thestarting resistance. Asleeve surrounds the shaft 4 and rests with itslower end against the top of the support 5. This sleeve is looselymounted, so as to rotate about the shaft 4,and has secured thereto athree-armed carrier 7, to the arms of which one of the sets ofbridging-contacts is secured. This carrier is secured to the sleeve 6 bymeans of aset-screw S or in any other suitable manner and, like thesleeve 6,rests with its lower edge adjacent to or in contact with thesupport 5. The other carrier 9 for the other set of bridgingcontacts isloosely mounted upon a sleeve 6 and rests upon the top of the carrier 7,as shown. The controller-handle is indicated at H and is secured in anysuitable manner to a sleeve I, loosely mounted upon the shaft 4. Thissleeve carries a hooked arm E, secured thereto by means of the set-screw10. The

hooked arm at its lower end carries a spring- O lh) actuatedlocking-pawl F, which operates in conjunction with a cam G and with twonotched plates Jand N. The cam Gris secured to the shaft 4 by means of aset-screw and in Fig. l is shown as consisting of two semicircularportions of different radius merged into each other. The notched disk Jis secured to the sleeve 6 and is thus fixed with respect to the carrier7, while the notched disk N is an integral part of the carrier 9. Thelockingpawl F carries an antifriction-roller X, which moves over theworking surface of the cam G and is urged against the same by means ofthe spring Y, connected at one end to a downwardly-projecting arm of thepawl F and at its other end to a finger formed integral with the hookedarm E.

In the position of parts indicated in Fig. 1 the locking-pawl F engagesthe notch in the disk J, while its antifriction-roller bearsupon thatportion of the working surface of the cam G nearest to the shaft 4. Theforward motion of the controller-handle thus causes the carrier 7 torotate by reason of the locking connection between thehooked arm E andthe disk J, this locking connection, as already described, being formedby means of the pawl F engaging a notch in the disk. After the carrierhas moved across all of the resistance-contacts and the outer or lastcontact of the series the antifriction-rolier X reaches that part of thecam-surfaceindicated at 11. The upper end of the pawl F is then thrownout, thus causing its lower end to move inwardly and engage the notch inthe disk N, attached to the carrier 9. As will readily be understood, areverse movement of the controller-handle will cause these operations tobe performed in the reverse order, so that whereas on its forward motionthe first operation of the controller is to insert resistance in theprimary member and gradually cut it out on the return motion, on thecontrary the last operation is to insert resistance l gradually and thenbreak the circuit of the Winding of said member.

Each arm of the carriers 7 and 9 carries a bridging-contact, which is ofthe character indicated in plan in Fig. 1 and more in detail in Fig; 2in section. Each carrier-arm has an extension 12 secured to the arm, butinsulated therefrom by means of suitable insulating'material 13. Carbonbrushes projecting down from the extension 12 are springpressed againstthe cooperating contacts by means of suitable springs 14, the tension ofwhich may be varied by adjusting-nuts 15.

The apparatus which I have thus shown for carrying out my invention isWell adapted to the purpose; but it will readily be understood that manymodifications of the same may be effected for securing the same end, andfor this reason I do not limit myself to the employment of theabove-described apparatus, but include within my invention all devicesthat may perform the same functions, even though the same be radicallydifferent in op- ICO IIO

eration, and although I regard the use of a single resistance both forstarting and for limiting the primary currentor stopping the motor as avaluable feature of my invention I do not wish to be limited thereto,since it is evident that, if desired, separate resistances may beemployed for the purposes mentioned. lWIy invention is therefore not tobe understood as restricted to the use of a single resistance.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. The combination with an induction-motor, of means fordissimultaneously varying the resistance of the circuits of the inducingand induced windings respectively.

2. The combination with an ind uction-motor, of a resistance, and meansfor inserting the resistance in circuit either with the inducing-Winding or with the induced Winding of the motor.

3. The combination with an induction-motor, of a resistance, and meansfor inserting the resistance first in circuit with the Windings of onemember of the motor, then in circuit With the windings ofthe othermember of the motor.

Li. The combination with an ind uction-motor, of means for inserting`resistance in the windings of either member oi' the motor.

5. The combination with an induction-motor, of means fordissimultaneously inserting resistance in circuit with the inducing andinduced windings of the motor.

6. The combination of two independentlymovable switch-arms, acontrolling-handle and operative connections therewith for causing apositive and successive engagement between the controlling-handle andthe switcharms.

7. The combination of contacts, a plurality of switch-arms each movableover said contacts and means for successively moving said switch-arms.

8. The combination of a plurality of switcharms,a controlling-handletl1erefor,and means for automatically disengaging the controllinghandlefrom one switch-arm and causing it to positively engage the otherswitch-arm.

In witness whereof I have hereunto set my hand this 5th day of June,1899.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULL, MABEL E. JAooBsoN.

